Today, motor vehicles include various electronic control units mounted in the vehicle. The control units may control various systems and/or subsystems within the vehicle. For example, a control unit may control an engine, the transmission, brakes or the steering mechanism. These control units are typically coupled to a variety of sensors and/or actuators.
Handheld diagnostic tools have been utilized to trouble-shoot faults associated with these control units. A typical diagnostic tool, for example, a scan tool, can include a microcontroller and an interface circuit to facilitate communication between the microcontroller and the control units in the vehicle. Each diagnostic tool can also include non-volatile internal or external memory, such as a plug-in module, that stores various diagnostic routines and/or vehicle diagnostic data or user configuration data to enable the tool to communicate with a vehicle's control unit as well as provide information to a user. The data being stored may include: fault codes that identify problem vehicle components; vehicle system data, for example, power train data, anti-lock break system (ABS) data, electrical system data, or sensor data, for example, vehicle temperature, revolutions per minute (rpm) data or pressure data.
Generally, diagnostic routines, user configuration data and the diagnostic data from the vehicle are stored in non-volatile memory having read and write privileges. Accordingly, the diagnostic tools may be configured with file systems to organize, segment and store the diagnostic routines or applications, user configuration data, and vehicle diagnostic data, for read and write capability. Although it is desirable to store the applications and data in read/write mode for later access, using file systems to store data can increase boot time to load a diagnostic tool's operating system and run its diagnostic applications. A high end or professional range scan tool can be configured to store, in addition to the data described above, vehicle specific data that is based, for example, on the make or model of the vehicle being examined. Moreover, the professional range scan tool can include embedded operating systems with file system support. Given the configuration of these high end scan tools, there exists an overhead or consumption of computer resources upon power up of the device, thus increasing boot time. This boot time can be as long as two minutes. This boot delay can therefore make the professional range scan tool unattractive for quick system checks, for example, to make a diagnostic code reading from a vehicle. As a result, automotive technicians will generally use a low end scan tool having limited capability, for example, a scan tool having only code reading capability in order to perform the quick system check.
An alternative technique to reduce boot time is to configure a scan tool such that the operating system and application file system is mounted in read only mode. However, the technique inhibits storing user data, including user configuration data, and retrieved vehicle diagnostic data in a file system for read/write mode and later access.
Accordingly, it is desirable to provide a method and apparatus for the storage of user configuration data and retrieved vehicle diagnostic data with read/write capability in a diagnostic tool having a boot time that is minimized or otherwise fast using a read-only file system. Moreover, it is desirable to provide such a diagnostic tool that is compatible with the operating features of a high end diagnostic tool.